I have a core 2 quad q9550, 8gb ram, with 560TI 1GB.
I hit around 30-40 FPS on first island, I tried changing settings to both low & high (including config tweaks) and did not see even a slight difference in negative acceleration.

But thanks for reply mate, is good to know this problem is not universal !
I actually suspect is my poor generic mouse with this particular game (no problems with other games), long due for an upgrade so will see if it helps ey.